1. Field
The present disclosure is related generally to a data processing system and in particular to a method and apparatus for rivet height gages. More particularly, the present disclosure is directed to a computer implemented method, apparatus, and computer usable program code for calibrating rivet height gages.
2. Background
Fasteners on commercial and military aircraft carry loads from one component of the aircraft to the next. A rivet is a commonly used mechanical fastener. At installation, a rivet is placed in a pre-drilled hole that may or may not be countersunk. The size and angle of the countersink should correspond to a particular countersunk rivet.
A countersunk rivet is a rivet having a conical shaped head with a substantially flat outer face and tapering inner face allowing the countersunk rivet to engage the countersink in the material. Typically, the installed outer face of the rivet sits substantially flush with the surrounding material.
If a countersink for the rivet is the wrong size, shape, or is misaligned relative to the rivet hole or surrounding material, the rivet may be difficult to install in the hole, may fit up improperly, or may be preloaded in a non-optimal manner. These conditions may be undesirable. In such cases, the head of the fastener may protrude above the surrounding surface further than desired, sit at an incorrect angle, or sit too low in the countersink. At aircraft speed, these protruding, misaligned, or too deep fastener heads may be undesirable.
Rivet height gages are distinct or specialized countersunk rivets manufactured to exacting tolerances. Rivet height gages are placed in countersinks and used to determine the location of a rivet head relative to the surrounding surface and/or the countersink.
In other words, rivet height gages are used to verify that rivet countersinks are drilled to a proper depth, angle, and/or size so the top of a particular countersunk rivet head will be substantially flush with the surface of the material being riveted when the rivet is inserted in the rivet hole. Consequently, rivet height gages may also be used to verify more accurate depths of rivets and fasteners through a material. Rivet height gages are used in the manufacture, construction, repair, and maintenance of a number of manufactured items, including, without limitation, aircraft and aerospace vehicles.
Rivet height gages are periodically calibrated to ensure that the device is correctly measuring the countersinks. Currently, rivet height gages are calibrated using rivet calibration gages having sharp edges, such as, without limitation, sharp edged ring gages and chamfer gages. The sharp edges on these rivet calibration gages may be subject to wear, smoothing, and rounding at the edges of the ring gage. This rounding or wearing of the sharp edge is referred to as “roll-off.” A rivet height gage calibrated using a rivet calibration gage with roll-off may protrude from the rivet calibration gage to a height that is less than it would protrude in the absence of the roll-off. As a result, every rivet of the size calibrated using a rivet calibration gage with roll-off, also called a worn ring gage, may protrude above the material further than expected and desired.
Moreover, the roll-off, also known as round-off, of the sharp edge on currently available rivet calibration gages may preclude a better rivet gage calibration. Currently, maintenance personnel can attempt to counteract the roll-off by using an abrasive to shape the calibration gage top surface in order to provide a slightly sharper edge. However, roll-off removal may be difficult and time consuming. Moreover, sharp-edges may frequently not be sharp enough even when the ring gage is new. Therefore, current solutions may be insufficient to counter the effects of roll-off.
The tolerance requirements for rivet height gages necessitate a better, more accurate rivet height gage calibration. Accordingly, there is a need for a method and apparatus for minimizing or eliminating the effects of roll-off in rivet height gage calibration, which overcomes the problems discussed above. Embodiments of the disclosure are intended to satisfy this need.